Viral disease is a significant health concern that threatens large segments of human populations. Some of the features related to viral infection which are of concern to health care professionals include its highly contagious nature (e.g., HIV, SARS, etc.) and high mutability. Some viruses are also oncogenic (such as HPV, EBV and HBV). While viruses are structurally amongst the simplest of organisms, they are regarded to be among the most difficult to control and present a formidable challenge for antiviral drug R&D.
Thus far, there have been a few antiviral drugs widely used in patients, such as Amantadine and Oseltamivir for influenza. Acyclovir for HSV-related infections, Ganciclovir for CMV infection, and multiple agents including co-formulated drugs (Efavirenz, emtricitabine, and tonfovir disoproxil fumarate) for AIDS treatments. These drugs possess a variety of undesirable neurological, metabolic and immunological side-effects. Therefore, development of new antiviral therapy has become a major focus of medical and pharmaceutical research and development.
Infection by hepatitis C virus (HCV) is a serious health issue. It is estimated that 170 million people worldwide are chronically infected with HCV. HCV infection can lead to chronic hepatitis, cirrhosis, liver failure and hepatocellular carcinoma. Chronic HCV infection is thus a major worldwide cause of liver-related premature mortality.
The present standard of care treatment regimen for HCV infection involves combination therapy with interferon-alpha and ribavirin, often with the addition of a direct-acting protease inhibitor (Telaprevir or Boceprevir). The treatment is cumbersome and sometimes has debilitating and severe side effects. For this reason, many patients are not treated in early stages of the disease. Additionally, some patient populations do not durably respond to treatment. New and effective methods of treating HCV infection are urgently needed.
The dominant therapeutic approaches that are currently employed to treat cancer include surgical removal of primary tumors, tumor irradiation, and parenteral application of anti-mitotic cytotoxic agents. Unfortunately, only a relatively small cross-section of cancer patients have tumors that are “addicted” to a specific pathway, and can therefore be treated with newer targeted agents. The continued dominance of these long established therapies is mirrored by the lack of improvement in survival rates for most cancers. In addition to limited clinical success, devastating side effects accompany classic therapies. Both radiation- and cytotoxic-based therapies result in the destruction of rapidly dividing hematopoietic and intestinal epithelial cells leading to compromised immune function, anemia, and impaired nutrient absorption. Surgical intervention often results in a release of tumor cells into the circulation or lymph systems from which metastatic tumors can subsequently be established. Improved methods for the treatment of cancer are needed.